Are there two coolant temperature sensors on 1990 Crown Victoria?
If you have an electric fan, plus the clutch fan, then the
answer is yes. The first sensor will give you the engine temp. The
2nd sensor, when the engine heats up more, will open the connection
to start the electric fan. If the gauge works on the dash, temp.
and all is normal, but the electric fan does not come on, then
replace the sensor for the fan. Just follow the wire to its
location. If you have a/c , as soon as you put it on, the electric
fan will start. If it does not, then check for a power loss at the
fan, fuse, or just have to replace the fan. Just pull the wire
harness off the sensor, jump the 2 wires, fan should start.